Ok, Resolution for me was to remove $lastDigit and also to add CONFIG:$RRD_DB_DIR into SNMP Poller to get it working.
As far as I see an issue:
Even if in SNMP Poller you will be able to determine lastDigit(what it can't as I can see) of farmId -> you have nothing to add(switch in server/statistics.php file) those xN1xN2 params. (in that case you will never able to get image for stats)
Also because you leave var_dump inside server output for stats:
#$farm_rrddb_dir = CONFIG::$STATISTICS_RRD_DB_DIR."/{$folder}/{$farminfo['id']}";
$farm_rrddb_dir = CONFIG::$STATISTICS_RRD_DB_DIR."/{$farminfo['id']}";
if ($watchername == 'ServersNum')
$rrddbpath = "{$farm_rrddb_dir}/{$role_name}/SERVERS/db.rrd";
else^M
$rrddbpath = "{$farm_rrddb_dir}/{$role_name}/{$watchername}/db.rrd";
#var_dump($rrddbpath);
it will never showed up to people as server can't process JSON answer from server